Ive just built this same circuit and appear to be having the exact same issue as Alvaro. Im a pretty experienced builder, but have gone over this build with a fine tooth comb and im happy with component placement and connections. Its obviously possible that Ive missed something, but the behaviour being the same as OP its got me wondering.
It sounds exactly like the wah is stuck in a single position. Ive tried every combination of the dials, and have tried to copy demos on youtube with knob placement. ive got bias as a pot on the front and it sweeps up and down and makes the fixed position more or less pronounced but it doesnt sweep on its own or in response to picking attack.
Im wondering if its got to do with a transistor not operating at the right voltage, or possibly with capacitor choice. Ill attach some photos to a new thread.
Any help is much appreciated.